John Loudon McAdam was a Scottish civil engineer and road-builder who lived from September 23, 1756, to November 26, 1836. He created a new method called "macadamisation" to build roads with a smooth, hard surface. This method used different-sized materials and a planned structure to make roads more durable and less muddy than paths made of soil.

Today’s road construction still shows McAdam’s influence. One major improvement later was adding tar, originally coal tar, to hold the road’s stones together. This combination became known as "tarmac," short for "tar macadam."

Early life

McAdam was born in Ayr, Scotland. He was the youngest of ten children and the second son of the Baron of Waterhead. As a child, he moved to Lagwine at Carsphairn to live with his grandparents. His family originally used the name McGregor, but they changed it to McAdam, claiming descent from the Biblical Adam, for political reasons during the reign of James VI.

In 1770, McAdam moved to New York. During the American Revolution, he worked as a merchant and prize agent, earning money by managing his uncle William McAdam’s counting house. He returned to Scotland in 1783 and bought an estate in Sauchrie, Ayrshire.

In addition to participating in local Ayrshire affairs, McAdam managed the Kaims Colliery. This colliery provided coal to the British Tar Company, owned by Archibald Cochrane, 9th Earl of Dundonald, and his business partners in the coal tar trade. McAdam operated the kilns used in the company’s work. He was also involved with the ironworks at Muirkirk, which used coke, a byproduct of the tar business. This connection is the only direct link between McAdam and the tar industry.

Career

In 1783, McAdam became a member of the Ayrshire Turnpike and took on more responsibilities in road building over the next decade. In 1802, he moved to Bristol, England, and became the general surveyor for the Bristol Corporation in 1804. He shared his ideas during Parliamentary investigations in 1810, 1819, and 1823. In two written works from 1816 and 1819, he explained that roads should be built higher than the ground around them and made with layers of rock and gravel in an organized way.

In 1816, McAdam was also named surveyor for the Bristol Turnpike Trust. He redesigned the roads under his care using crushed stone covered with gravel on a solid base of large stones. A slight curve in the road, called a camber, helped rainwater drain quickly, preventing damage to the road’s base. This method, the most significant improvement in road building since Roman times, became known as "macadamisation" or "macadam."

The macadam method spread rapidly worldwide. The first macadam road in North America, the National Road, was completed in the 1830s. By the end of the nineteenth century, most major roads in Europe had been rebuilt using McAdam’s process.

Although McAdam earned £5,000 for his work with the Bristol Turnpike Trust and was named "Surveyor-General of Metropolitan Roads" in 1820, professional jealousy caused the UK Parliament to reduce a £5,000 expense grant to £2,000 in 1827. His effective road-building and management exposed dishonest practices by some turnpike trusts, which collected high tolls but often operated at a loss.

Death and descendants

McAdam died in Moffat, Dumfriesshire, while traveling back to his home in Hoddesdon, Hertfordshire, after his yearly summer trip to Scotland. His three sons, and later, his four grandsons, followed him into the same profession and helped manage road organizations called turnpike trusts across the country. His second surviving son, James Nicoll McAdam, known as the "Colossus of Roads," was given a knighthood for managing turnpike trusts. It is said that a knighthood had once been offered to his father but was refused.